Use Batch File Processing To Remove Last Character - batch-file

Question

I have a process where an incoming file is csv and has trailing commas after the last entry.
I need to process this and send it out sans that final comma as it causes a verification error with the phantom "empty column"
Currently I've got this piece of code to write each line into a new file:
for /f "tokens=* delims=" %%x in (file.csv) do echo %%i >> test.txt
And I've been trying to use something like echo %string:~0,-1% to remove the trailing comma in conjunction but I'm not having much luck. I don't think %%i can be used the same as a string would be referenced with the above. I've tried writing %%i into a string but seems I've got that syntax wrong too.
[edit]
I do run the file through a vbs script to replace the commas with pipes (, = |) so if there's an easier way to do it as part of that process, in my searching of stackoverflow to try and resolve this prior to asking I found this line which I thought may help:
strNewText = strNewText.Substring(0,strNewText.Length-1)
strNewText being the variable holding the updated data, doesn't work though, now the find and replace text section doesn't actually run when I add that in:
rem CREATE Find And Replace Text VBS SCRIPT
echo Const ForReading = 1 > "%tmp%\fart.vbs"
echo Const ForWriting = 2 >> "%tmp%\fart.vbs"
echo strFileName = Wscript.Arguments(0) >> "%tmp%\fart.vbs"
echo strOldText = Wscript.Arguments(1) >> "%tmp%\fart.vbs"
echo strNewText = Wscript.Arguments(2) >> "%tmp%\fart.vbs"
echo Set objFSO = CreateObject("Scripting.FileSystemObject") >> "%tmp%\fart.vbs"
echo Set objFile = objFSO.OpenTextFile(strFileName, ForReading) >> "%tmp%\fart.vbs"
echo strText = objFile.ReadAll >> "%tmp%\fart.vbs"
echo objFile.Close >> "%tmp%\fart.vbs"
echo strNewText = Replace(strText, strOldText, strNewText) >> "%tmp%\fart.vbs"
echo strNewText = strNewText.Substring(0,strNewText.Length-1) >> "%tmp%\fart.vbs"
echo Set objFile = objFSO.OpenTextFile(strFileName, ForWriting) >> "%tmp%\fart.vbs"
echo objFile.WriteLine strNewText >> "%tmp%\fart.vbs"
echo objFile.Close >> "%tmp%\fart.vbs"
(all the echo's are because I generate the vbs during the batch runtime, I tend to find things easier when everything's done in the one file, this vbs file is then deleted later in the process).

Answer 1

#if (#This==#IsBatch) #then
#echo off
rem **** batch zone *********************************************************
type inputfile.csv | cscript //nologo //e:javascript "%~f0" > outputfile.csv
exit /b
#end
// **** Javascript zone *****************************************************
while (!WScript.StdIn.AtEndOfStream) WScript.StdOut.WriteLine(WScript.StdIn.ReadLine().replace(/,[\s,]+$/,''));
This is an hybrid batch/javascript file. Save as batch file, execute and the inputfile.csv file will be piped into cscript.exe that will execute the javascript code included in the same batch file, iterating over the piped data and deleting all commas and final spaces from last comma to end of line. Output from pipe is sent to outputfile.csv
EDITED - As stated in comments, maybe i missunderstood the question, and it is not necessary to remove commaS at the end of the lines, but only the final comma. In this case, the replace expression should be
... .replace(/,$/,''));

Answer 2

Probably the simplest solution for your problem would be sed for Windows:
C:\>sed "s/,$//" <in.csv >out.csv
You could also write a simple VBScript that does the same thing:
Set re = New RegExp
re.Pattern = ",$"
Do Until WScript.StdIn.AtEndOfStream
WScript.Echo re.Replace(WScript.StdIn.ReadLine, "")
Loop
Usage:
C:\>cscript //NoLogo script.vbs <in.csv >out.csv
PowerShell would be an even better option:
PS C:\> (Get-Content 'in.csv') -replace ',$' | Out-File 'out.csv'
I would not recommend using batch for this.

Answer 3

I'm not sure this will work, but since you only want the code to apply for the last line, I've tried implementing the code differently from your average for loop.
#echo off
setlocal enabledelayedexpansion
set previous=
set current=
ren file.csv file.tmp
3<file.tmp (
:loop
set previous=!current!
set /p current=<&3
if "!current!" == "!previous!" (
Echo !current:~0,-1! >> file.csv
) Else (
Echo !current! >> file.csv
goto :loop
)
)
type file.csv
Echo. &Echo Only delete if file.csv is not corrupt
del /p file.tmp
Endlocal
And that should about do what you want.
Mona.